Such subjects are already known from the application DE 10 2006 041 467 A1. That application describes a procedure for operating a combustion engine, at which fuel is directly injected into a cylinder and chemically converted with air. The combustion of the fuel takes place by an Otto-motoric self-igniting procedure.
The Otto-motoric self-ignition (controlled auto ignition—CAI) provides a high potential for a fuel consumption reduction at simultaneously low emissions in partial load. This combustion procedure is therefore intensively examined at this point of time. A homogenous air-fuel-mixture is compressed at the Otto-motoric self-ignition. It ignites itself as soon as a sufficiently high temperature and a corresponding pressure in the combustion chamber are achieved.
The temperature of the mixture that is required for the self-ignition of the air-fuel-mixture is achieved by retaining hot remaining gas from the previous working cycle in the cylinder. Such an exhaust gas retaining is thereby achieved, in that a variably controllable outlet valve of the cylinder is closed long before reaching the gas change upper dead point and in that the hot remaining gas in the cylinder is compressed. The inlet valve opens for the fresh air supply only when there is inlet manifold pressure in the cylinder in order to avoid load losses.
The application DE 10 2006 041 467 A1 describes a regulation concept, at which the self-ignition of the air-fuel-mixture is controlled by a variable separation of the fuel amount that has to be injected into a cylinder during one work cycle to a pre-injection and a main injection. The pre-injection takes place before the upper dead point of the gas change, and the main injection takes place during the subsequent suction phase. The temperature of the cylinder filling that is achieved at the end of the subsequent compression increases according to DE 10 2006 041 467 A1 with an increasing rate of the pre-injection. A difference of ca. 60 K has been observed in the compression end temperature at the variation of the rate of the pre-injection between 0% and 10%.
For controlling the combustion the regulator concept of DE 10 2006 041 467 A1 provides a combination of a regulator for the induced average pressure, a lambda regulator and a regulator for the combustion position.
The regulator for the induced average pressure emits the main injection duration as correcting variable and therefore the fuel amount that is injected with the main injection. The load is regulated by this correcting variable. In other words: The desired torque is adjusted by the correcting variable.
The lambda regulator processes the signal of a lambda probe into a correcting variable, with which the phase position of an intake camshaft and therefore the remaining gas rate in the cylinder can be adjusted.
The regulator for the combustion position works with the 50% conversion point of the heating course as input variable. At a position of the 50% conversion point that is too late the pre-injection duration is increased, while it is lowered if the position is too early. The position of the 50% conversion point is derived from the cylinder individual combustion chamber information, which is provided by the cylinder individual cylinder pressure sensors or ion current sensors.